<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // let sum = [88,20,10,100,50]
        let sum = [88,20,30,100,50]
        let put = -1
        for(let i = 0 ; i < sum.length ; i++ ){
            if(sum[i] === 10){
                put = i
            }
        }
        console.log(put);

        
    </script>
</body>
</html>